1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus, and more particularly, to an electrophotographic image forming apparatus having a waste toner sensing unit which senses whether a waste toner container is mounted, the amount of waste toner, and contamination of the waste toner container.
2. Description of the Related Art
In general, an electrophotographic image forming apparatus is a device which forms an electrostatic latent image on a photosensitive medium by exposing the photosensitive medium charged by a charger using light irradiated from a laser scanning unit (LSU) in response to a print signal, develops the electrostatic latent image with a developing agent supplied by a developing unit, forms an image, and transfers the image onto paper, thereby obtaining a desired image.
The developing agent, which is used to develop the electrostatic latent image and to form the image in the electrophotographic image forming apparatus, is composed of toner in a powder state and a liquid carrier.
The toner is attached to the electrostatic latent image and is used to form the electrostatic latent image as an image. In this case, all of the toner attached to the electrostatic latent image is not transferred from the photosensitive medium to a transfer unit or from the transfer unit to paper, and a part of the toner remains on the photosensitive medium or the transfer unit.
The toner remaining on the photosensitive medium or the transfer unit is removed by an additional cleaning unit and stored in a waste toner container by a removing unit.
Meanwhile, the liquid carrier is removed by an additional carrier removing unit. In particular, a color developing unit uses a developing agent of four colors, such as yellow, cyan, magenta, and black, and thus, the amount of waste toner increases compared to a developing unit using a single color. Thus, a time for replacing the waste toner container needs to be checked by sensing the amount of waste toner stored in the waste toner container, and whether the waste toner container is mounted needs to be sensed.
An apparatus for sensing the amount of waste toner stored in a waste toner container is disclosed in U.S. Pat. No. 4,099,861 and Japanese Patent Publication No. JP 07-271116, the entire contents of which are incorporated herein by reference.
FIG. 1 illustrates a structure of a conventional waste toner sensing apparatus. Waste toner 120 removed by a waste toner removing unit (not shown) is stored in a waste toner container 100 through an intake 110. The waste toner sensing apparatus includes a light-emitting portion 150 for radiating light and a light-receiving portion 160 for receiving light irradiated from the light-emitting portion 150. The light-emitting portion 150 and the light-receiving portion 160 are installed opposite to each other wherein the waste toner container 100 is placed therebetween and below.
A switch 170 is separately installed under the waste toner container 100. The switch 170 is turned on or off when the waste toner container 100 is mounted in or detached from a main body, intercepts light irradiated from the light-emitting portion 150, and indicates whether the waste toner container 100 is mounted.
If light irradiated from the light-receiving portion 150 hits the waste toner 120 stored in the waste toner container 100, the light is not received by the light-receiving portion 160. Thus, when there is a difference between the amount of light that does not hit the waste toner 120 and is normally received by the light-receiving portion 160, and the amount of light received by the light-receiving portion 160 that has not hit the waste toner 120, the waste toner 120 is sensed. In this case, as the amount of light received by the light-receiving portion 160 becomes smaller, the greater the amount of waste toner stored in the waste toner container 120.
However, the waste toner 120 may be attached to an inner side 101 of the waste toner container 100. The waste toner 130 attached to the inner side 101 of the waste toner container 100 serves to intercept light irradiated from the light-receiving portion 150 so that the light is not received by the light-receiving portion 160. Accordingly, since the waste toner 130 is attached to the inner side 101 of the waste toner container 100, the waste toner 120 may erroneously be sensed to have completely filled the waste toner container 100.